The Uncertain Future of the International Space Station: Analysis

Still unfinished, engineers around the world ponder what to do with the space station—park it somewhere else, turn it into a lab or just let it burn. With calls to upconvert the ISS into a spaceship already hitting fever pitch, a leading aerospace expert checks in with some players from the space industry.

The International Space Station isn't scheduled to be completed for two more years, but a growing chorus of engineers and executives is already brainstorming about what to do with the ISS after its life span ends in 2015. Given how long it has taken to put together the actual pieces in space--the Japanese experiment module Kibo was finally installed just a few weeks ago--and the tens of billions of dollars sunk into the station, it's understandable that many would like to see the working power of the ISS extended to 2020 or beyond. Plans range from the humble, like guiding it into a fiery reentry, to the ludicrous, like driving the station to the moon and parking it there.

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I say ludicrous because of the complex engineering issues involved with rethinking the space station's life span. It is, after all, made up of many separate pieces that have been delivered and assembled at different times. The original core, the Russian Zarya module, has a rated lifetime on orbit of 15 years, but it was launched almost 10 years ago and should be removed and deorbited in 2013. In practice, of course, space hardware often lasts long past its design life, and there may be ways of refurbishing those things on orbit (e.g., seals) that might degrade, while the basic structure remains sound. Nonetheless, an aging station will raise the same issues that are currently forcing the space shuttle into retirement to avoid an expensive "recertification"--particularly since no one really knows what that means, since it was never "certified" in the first place.

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Will China, Russia or Hoteliers Close in on a Post-U.S. ISS? The biggest immediate problem with operating toward an indefinite future is a basic one: transportation to change out crews and deliver cargo such as food, water and clean clothes. After the shuttle is retired (planned for 2010), the only available way of getting to the ISS will be the Russian Soyuz, which is currently in use. NASA says its new Orion/Ares launch system could resupply ISS when it's ready in 2015, but there are doubts that NASA will be involved with the station past 2015. The agency remains noncommittal; the United States government has no policy covering the ISS's retirement. "[Michael Griffin] has said that he'd like to see it continue beyond that period, but that's a decision for the next administration, or perhaps the one after it," says NASA spokesman John Yembrick, "There is no specific plan for the facility after 2015." (As I outlined for PM earlier this year, John McCain and Barack Obama's space policies have begun to lay out ideas on that front.)

If America's focus on the moon and Mars removes the U.S. from the ISS partnership, there would be nothing to keep the remaining partners from bringing in new players, such as China, with their own resupply capabilities. The station's foreign partners and other stakeholders recently met to discuss the issue. And there's real interest from the Europeans and Japanese in developing their own independent capabilities to provide crew and cargo transfer. European countries are also talking to Russia about a joint effort for a new crew vehicle.

Some space program proponents want to see the United States stay involved with the ISS. "I'd like to think that we will continue to support it and participate actively," says Marty Hauser, vice president of operations research and analysis for the Space Foundation, an advocacy group based in Colorado Springs. "It is a good model for an international alliance that we may ultimately need to see [the planned U.S. trip to the moon and Mars] to fruition, given how expensive it is going to be. We may not be able or willing to afford it on our own."

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Hauser adds that the ISS could be used to support NASA's moon and Mars missions, noting that it could be used for simulating long-duration, deep-space missions and as a long-term testbed for needed exploration technologies, in addition to its planned use as a weightless research facility.

Another player who wants to see the ISS continue on well past its sell-by date is Tom Pickens, son of famous oilman T. Boone Pickens and CEO and chairman of Spacehab. The company recently signed an agreement with NASA to use the ISS for biological and other weightless-environment research, and for some space on a few of the remaining shuttle flights for final assembly of the station. "The ability to utilize the unique microgravity environment for industrial processing purposes is expected to revolutionize a myriad of industries," he argues. "We believe the utilization of the ISS as a national lab will have a significant social and economic impact and shows great promise of saving lives and providing thousands of new jobs in the coming years.'

It would make sense for Robert Bigelow, whose company is building a space station for private use, to be interested in using the ISS as a hotel, but Bigelow Aerospace would rather build from scratch. "We're pretty focused on building our own, for our own purposes in our own orbits," said Chris Reed, director of publicity for the company. "That's keeping us pretty busy without thinking about using the ISS."

Can Engineers Really Move the ISS?

Earlier this month, Michael Benson jump-started a lot of the public talk about the real future of the ISS in an op-ed for The Washington Post. Deciding that the station is simply in the wrong place, Benson proposed that it be refitted as an interplanetary spaceship.

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Benson's idea suffers from several flaws. The ISS is designed for operations in low Earth orbit (LEO), but that is a unique environment. Had trips beyond that altitude been the station's intended use, both the requirements and the design would have looked very different. Tom Jones, a four-time shuttle astronaut and PM's guru on space who's looked at the future of the ISS here before, notes that the station is designed for LEO and should stay there: "It isn't designed to operate for long periods of time without resupply of things like food, water and spare parts for maintenance. You'd have to develop a duplicate interplanetary system anyway just to deliver the supplies and rotate the crew."

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Another flaw to making the station a spaceship is a lack of radiation shielding: Once out of LEO, the crew and the electronics, including solar panels, would be vulnerable to normal radiation levels and spikes caused by solar flares. Picking a thruster that will not damage the ISS's structure is another major challenge.

But there's a more plausible potential relocation: In order to get a useful amount of cargo to the ISS with the space shuttle, the station is saddled with a lower altitude than would be optimal. This low orbit produces more atmospheric drag and less time for the solar panels to spend in daylight. Also, more damage is done to the structure by monatomic oxygen in the upper atmosphere, which reacts with and "rusts" it over time. Other rockets, because their upper stages are so much smaller than the shuttle orbiter, are much less sensitive, and there isn't as much payload penalty for them to go higher. So it's likely that, with the retirement of the shuttle, the nominal orbit of the space station will be raised in altitude, reducing corrosion and increasing the amount of energy that the panels can collect per orbit.

What Will the Dying Days Look Like?

So far, all space stations ever built have met a fiery end, burning up in the atmosphere--with a few pieces even reaching the ground. If nothing is done to save it, the ISS will suffer the same fate. According to the 1967 Outer Space Treaty, to which the U.S. is a signatory, the U.S. government is responsible and liable for all objects put into space by U.S. entities, governmental or commercial. If title and keys of the ISS were to be transferred to some other public or private organization, the responsibility would remain with the U.S. government. If it is handed to another government, that government would be responsible.

A derelict space station is a hazard to others sharing its orbit, and eventually, its orbit will decay if control is not maintained--and it could come down anywhere. That was the case when Skylab, America's first space station, had a violent retirement in 1979. The station had no systems aboard to deorbit it on command, so it spiraled down, slowly at first and then rapidly as it got into thicker air. Several large pieces crashed in Australia, without injury or property damage. But an ISS death trip will be controlled similar to the way the Russian Mir station came back to earth. The Russians brought Mir brought down deliberately with a deorbit burn that aimed the station at an uninhabited part of the South Pacific. Like Skylab, it became a major cultural event, with Taco Bell, in a publicity stunt, floating a large target in the ocean and promising free tacos for a day if any pieces hit it. While such things are not precise, they did a pretty good job of it, with the biggest pieces landing in the ocean near Fiji. No one got any free tacos.